Gas flow sound attenuation device

ABSTRACT

The gas flow sound attenuation device includes a number of variations each having at least one pressure pulse reflecting chamber, i.e., a Helmholtz chamber, installed in axial alignment with the upstream gas flow. Gas flow is transferred laterally externally to the chamber, with the single opening of the chamber receiving substantially all incoming pressure pulse energy to maximize the reflection and canceling of those pulses back into the upstream duct. The device may incorporate any practicable number of chambers, so long as each has at least some length of upstream pipe or duct axially aligned with the chamber opening. The chambers may have any practicable shape and/or may include internal baffling. The device may be applied to any gas flow system, e.g., heating, ventilation, and air conditioning systems, but is particularly effective in reducing the sound output of internal combustion engine exhaust systems.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to systems and devices for reducing sound emissions due to the dynamic flow of gases through ducts, pipes, and the like, such as in exhaust and intake systems for internal combustion engines, heating, air conditioning, and ventilation systems, etc. More specifically, the present invention relates to a gas flow sound attenuation device having at least one Helmholtz chamber, i.e., a resonant chamber, having only a single opening axially aligned with the upstream gas flow and pressure pulses, rather than axially offset therefrom.

2. Description of the Related Art

The production of audible sound or noise from a moving gas stream is a well-known phenomenon. The effect can make itself known even where no combustion occurs, with the effect being utilized for the production of sound in all wind instruments in the musical field. However, in other fields it may be more desirable to reduce or cancel the sound or noise produced by the moving gas stream, e.g., in air intake systems, heating, air conditioning, and ventilation systems, etc. This is particularly true where additional sound is generated by combustion of a fuel with the gas, as in an internal combustion engine.

Conventionally, sound produced by internal combustion engines is controlled by means of mufflers and resonators, with some sound reducing effect perhaps being due to additional componentry, such as turbochargers and catalytic converters, installed in the exhaust system. Mufflers are the primary means for reducing sound emissions from internal combustion engines, with resonators primarily employed to cancel certain limited frequencies. Other components have relatively little effect. A great deal of research and development has gone into muffler technology over the years, but essentially all mufflers incorporate a labyrinth pathway through which the gas must flow, with a corresponding loss of energy, and therefore sound, in the gas flow as it passes through the muffler.

The corresponding increase in static pressure (back pressure) as the gas loses dynamic pressure (velocity) through the muffler is an undesirable side effect of muffler technology. As a result, various alternatives have been applied to mufflers, exhaust systems, and gas flow paths in general, in attempts to reduce the sound level while avoiding a corresponding increase in back pressure. Attempts have been made to reduce back pressure while simultaneously reducing sound output by means of a Helmholtz chamber, i.e., a chamber having a single opening therein. The chamber is joined to the gas passageway, with the theory being that pressure pulses in the system will travel into the chamber and will be reflected back out the single opening of the chamber to cancel incoming pressure pulses.

Obviously, a chamber having only a single opening must allow for gas flow therearound or thereby, as there can be no net flow through a chamber having only a single opening. As a result, the prior art has laterally offset such Helmholtz chambers from the primary gas pathway, with the gas tending to flow past the opening to the chamber. While this optimizes the gas flow, this axial offset of the chamber results in only a relatively small portion of the pressure pulse being reflected from the lip of the offset opening of the chamber. This may result in the sound actually being amplified at certain frequencies, and, in fact, this is the general principle used in all woodwind musical instruments and pipe organs, albeit using open airflow paths. A more specific example of the resonance caused by a Helmholtz chamber having an opening axially offset to the airflow path is found in the simple concept of blowing across the open mouth of a bottle, with the production of sound from this action being well known.

Thus, a gas flow sound attenuation device solving the aforementioned problems is desired.

SUMMARY OF THE INVENTION

The gas flow sound attenuation device is exemplified by various embodiments, which each include at least one Helmholtz chamber having its single opening axially aligned with the upstream gas flow, with the gas flow path being deflected or angled laterally from this alignment to allow gas to flow around the chamber. In this manner the chamber directly receives all incoming pressure pulses, or in other words all sound, emanating from upstream in the pipe or duct and reflects those pressure pulses directly back upstream into the incoming pulses. This serves to cancel at least some of the pressure pulses as they travel through the pipe, thereby reducing the sound output of the system, with the gas flow continuing through a lateral branch to the side of the chamber to exit downstream with no appreciable increase in back pressure.

The gas flow sound attenuation device may be applied to internal combustion engine exhaust systems and other systems where no combustion occurs, e.g., heating, ventilating, and air conditioning duct systems, etc. The chamber(s) may be formed of relatively low temperature materials, even when used in engine exhaust systems, as it has been found in testing that the temperatures of the relatively static gases that collect within the chamber are relatively low in comparison to the dynamic gas flow through the pipe. The device may include one or more chambers, so long as each is axially aligned with the immediate upstream flow path so that pressure pulses traveling down that path will pass directly into the chamber, rather than having the majority of the pulse energy bypass a laterally displaced chamber. The chamber or chambers may be a relatively simple cylindrical canister or canisters, or may incorporate various shapes to alter the effects on the pressure pulses. The chamber(s) may be devoid of internal structure, or may include internal baffling or the like in order to alter the effects.

These and other features of the present invention will become readily apparent upon further review of the following specification and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an environmental side elevation view in partial section of a gas flow sound attenuation device according to the present invention incorporated into a vehicle exhaust system.

FIG. 2 is a side elevation view in section of a prior art gas flow system incorporating a laterally disposed chamber.

FIG. 3 is a top plan view of an alternative embodiment of a gas flow device according to the present invention incorporating two symmetrically disposed chambers in a gas flow system having a bifurcated flow path.

FIG. 4 is a top plan view of another alternative embodiment of a gas flow sound attenuation device according to the present invention incorporating a single centrally disposed chamber into a gas flow system having a bifurcated flow path.

FIG. 5 is a top plan view of another alternative embodiment a gas flow sound attenuation device according to the present invention having multiple asymmetrically disposed sound attenuation chambers in a gas flow path.

FIG. 6 is a top plan view of another alternative embodiment of a gas flow sound attenuation device according to the present invention with the sound attenuation chamber having orthogonal branches.

FIG. 7 is a top plan view of another alternative embodiment of a gas flow sound attenuation device according to the present invention incorporating a branched chamber.

FIG. 8 is a top plan view of another alternative embodiment of a gas flow sound attenuation device according to the present invention having an alternative branched chamber.

FIG. 9 is a perspective view of an alternative chamber for a gas flow sound attenuation device according to the present invention, showing its alternative external shape.

FIG. 10 is a perspective view of another alternative chamber for a gas flow sound attenuation device according to the present invention, showing its alternative external shape.

FIG. 11 is a broken away perspective view of a muffler having multiple sound attenuation devices of the present invention incorporated therein, showing the internal configuration thereof.

FIG. 12 is a broken away perspective view of a gas flow sound attenuation device according to the present invention having an internally baffled chamber.

FIG. 13 is a broken away perspective view of another alternative embodiment of a gas flow sound attenuation device according to the present invention having an internally baffled chamber.

Similar reference characters denote corresponding features consistently throughout the attached drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention comprises various embodiments of a gas flow sound attenuation device, wherein a pressure pulse reflecting chamber having a single opening therein is installed in axial alignment with the upstream pipe or duct in order to accept substantially all of the incoming pressure pulse or sound energy from the upstream direction. In each case, the chamber has a larger volume than the inlet tube or pipe, thereby defining a Helmholtz resonant chamber. The device is applicable to virtually any system where gases are moved through a pipe, duct, tube, or other closed passageway, but is particularly useful in quieting the sound output from internal combustion engine exhaust systems.

FIG. 1 of the drawings illustrates an exemplary internal combustion engine exhaust system 110 incorporating a gas flow sound attenuation device according to the present invention. The system 110 extends from an upstream exhaust gas manifold 112, which would be attached to a conventional internal combustion engine to receive exhaust gas outflow therefrom during operation of the engine. A downpipe 114 connects the manifold 112 to a catalytic converter 116, with a muffler 118, resonator, or the like extending downstream from the catalytic converter 116.

An elongate exhaust gas flow passageway 120 has an inlet end 122 extending from the downstream end of the muffler 118, and an opposite outlet end 124. The passageway 120 includes an upstream portion 126 disposed between its inlet end 122 and its outlet end 124, and a stub portion 128, which is axially aligned with the upstream portion 126. The stub portion 128 includes an inlet end 130 in gas flow communication with the upstream portion 126, and an opposite outlet portion 132. The downstream portion 134 of the passageway 120 is axially offset from the upstream portion 126 thereof, with the outlet end 124 of the passageway extending from the downstream portion 134 thereof.

A sound canceling chamber 136 has a single opening 138 in communication with the outlet end 132 of the stub 128 and upstream portion 126 of the passageway 120, with the chamber 136 and its opening 138 being in axial alignment with the stub 128 and upstream portion 126 of the passageway 120, as indicated by the axial centerline A. This allows the chamber 136 to receive incoming pressure pulses P1, and reflect those pulses back up the upstream portion 126 of the passageway 120 as reflected pulses RP1. The reflected pulses RP1 tend to cancel the downstream traveling pulses P1, thus reducing the sound output of the exhaust system 110. Exhaust gases are free to travel through and leave the system by means of the axially offset downstream portion 134 of the passage 120, as indicated by the exhaust gas arrows G1 in FIG. 1.

FIG. 2 is an illustration of an exemplary prior art system, in which a Helmholtz chamber C is axially offset from the remainder of the pipe or passage P. It will be noted in FIG. 2 that very little of the downstream pressure pulses P2 are reflected back in the upstream direction as reflected pulses RP2. This is because the downstream traveling pulses P2 generally bypass the structure of the chamber C and its opening O, due to the alignment of the pipe P bypassing the offset chamber C and its opening O. Only very little of the pressure pulse is reflected back upstream as the peripheral edge of the pulse contacts the lip of the opening O for the chamber. Accordingly, very little noise or sound canceling effect is provided by such a configuration. This is typical of such configurations, as they are normally intended to produce or amplify sounds by the resonation of the air mass within the chamber C, rather than aligning the chamber with the upstream pulses to reflect back and cancel their energy.

FIG. 3 of the drawings illustrates another embodiment of a gas flow sound attenuation device 310 having a single upstream pipe 314 from the conventional exhaust system (not shown in FIG. 3), the gas flow path bifurcating and terminating in a pair of downstream passages 334 a, 334 b and their respective outlet ends 324 a, 324 b. Two gas flow passageways 320 a and 320 b branch from the downstream end of the upstream pipe 314. Each of the passageways 320 a, 320 b has an inlet end, respectively 322 a and 322 b, extending from the downstream end of the upstream pipe or passage 314, and an opposite outlet end, respectively 324 a and 324 b. Each passageway 320 a, 320 b includes an upstream portion, respectively 326 a and 326 b, disposed between its respective inlet end 322 a, 322 b and outlet end 324 a, 324 b.

Each passageway further includes a stub portion, respectively 328 a and 328 b, which is axially aligned with its respective upstream portion 326 a, 326 b. The stub portions each include an inlet end, respectively 330 a and 330 b, in gas flow communication with the respective upstream portions 326 a, 326 b, and an opposite outlet portion, respectively 332 a and 332 b. The downstream portions 334 a, 334 b of the passageways 320 a, 320 b are axially offset from the respective upstream portions 326 a, 326 b thereof, with the outlet ends 324 a, 324 b of the passageways extending from their respective downstream portions 334 a and 334 b thereof.

Each of the passageway stub portion ends 332 a, 332 b has a sound canceling chamber, respectively 336 a and 336 b, extending therefrom. Each chamber has a single opening, respectively 338 a and 338 b, in communication with the outlet end 332 a, 332 b of the respective stub 328 a, 328 b and upstream portion 326 a, 326 b of the respective passageway 320 a, 320 b. Each chamber 336 a, 336 b and respective opening 338 a, 338 b is in axial alignment with the respective stub 328 a, 328 b and upstream portions 326 a, 326 b of the passageways 320 a, 320 b, as indicated by the axial centerlines A. This configuration allows each of the chambers 336 a, 336 b to receive incoming pressure pulses from their respective axially aligned gas flow passages 320 a and 320 b and reflect those pulses back up the respective upstream portion 326 a, 326 b of the passageways, generally as described for the single sound canceling chamber embodiment of FIG. 1.

FIG. 4 of the drawings illustrates yet another embodiment of a gas flow sound attenuation device 410 having a single upstream pipe 414 extending from the conventional exhaust system, with the flow path bifurcating and terminating in a pair of downstream passages 434 a, 434 b and their respective outlet ends 424 a, 424 b. In the embodiment of FIG. 4, a single gas flow passageway 420 is axially aligned with, and extends from, the downstream end of the upstream pipe 414. The passageway 420 has an inlet end 422 extending from the downstream end of the upstream pipe or passage 414, an opposite outlet end 424, and an upstream portion 426 disposed between the inlet and outlet ends.

The passageway 420 further includes a stub portion 428, which is axially aligned with the upstream portion 426. The stub portion includes an inlet end 430 in gas flow communication with the upstream portion 426, and an opposite outlet portion 432. The downstream portions 434 a and 434 b of the passageways 420 a and 420 b are axially offset from the upstream portion 426 thereof, with the outlet ends 424 a and 424 b of the passageways extending from the respective downstream portions 434 a and 434 b thereof.

The passageway stub portion end 432 has a sound-canceling chamber 436 extending therefrom. The chamber has a single opening 438, in communication with the outlet end 432 of the stub 428 and upstream portion 426 of the passageway 420. The chamber 436 and its opening 438 are in axial alignment with the stub 428 and upstream portion 426 of the passageway 420, as indicated by the axial centerline A. This configuration allows the chamber 436 to receive incoming pressure pulses from the axially aligned gas flow passages 420 and reflect those pulses back up the respective upstream portion 426 of the passageway, generally as described for the single sound canceling chamber embodiment of FIG. 1.

FIG. 5 of the drawings illustrates a further embodiment of a gas flow sound attenuation device 510 having a single upstream pipe 514 extending from the conventional exhaust system, with the flow path terminating in a single downstream passage 534 and single outlet end 524 at the end of the downstream passage 534. A first gas flow passageway 520 a branches from the downstream end of the upstream pipe 514, with a second passage 520 b branching from the first passage and a third passage 520 c branching from the second passage. The downstream passage 534 branches from the third passage 520 c. Each of the passageways 520 a through 520 c has an inlet end, respectively 522 a through 522 c, extending from the pipe or passage immediately upstream thereof, e.g., passageway 520 a extends from the upstream pipe 514 with passageway 520 b extending from passage 520 a, etc. Each of the passages further has an opposite outlet end, respectively 524 a through 524 c. Each passageway 520 a through 520 c includes an upstream portion, respectively 526 a through 526 c, disposed between its respective inlet end 522 a through 522 c and outlet end 524 a through 524 c.

Each passageway further includes a stub portion, respectively 528 a through 528 c, which is axially aligned with its respective upstream portion 526 a through 526 c. A further stub portion 528 is axially aligned with the upstream pipe 514. The stub portions each include an inlet end, respectively 530 through 530 c, in gas flow communication with their respective upstream portions 514 and 526 a through 526 c, and an opposite outlet portion, respectively 532 through 532 c. The downstream portions of the system, i.e., passageway 520 a stemming from pipe 514; passage 520 b stemming from passage 520 a; passage 520 c stemming from passage 520 b; and outlet passage 534 stemming from passage 520 c, are axially offset from the respective upstream portions 514 and 526 a through 526 c thereof, with the outlet ends 524 a through 524 c of the passageways extending from their respective downstream portions 534 a through 534 c thereof.

Each of the passageway stub portion ends 532 through 532 c has a sound canceling chamber, respectively 536 through 536 c, extending therefrom. Each chamber has a single opening, respectively 538 through 538 c, in communication with the outlet end 532 through 532 c of the respective stub 528 through 528 c and upstream portion 514 and 526 a through 526 c of the respective passageway. Each chamber 536 through 536 c and respective opening 538 through 538 c is in axial alignment with the respective stub 528 through 528 c and upstream portions 514 and 526 a through 526 c of their passageways, as indicated by the axial centerlines A. This configuration allows each of the chambers 536 through 536 c to receive incoming pressure pulses from their respective axially aligned gas flow passages 514 and 520 a through 520 c and reflect those pulses back up the respective upstream portion 514 and 526 a through 526 c of the passageways, generally as described for the single sound canceling chamber embodiment of FIG. 1.

FIG. 6 shows a relatively simple gas flow sound attenuation device 610 having a configuration much like that of the system 110 of FIG. 1, but incorporating a branched sound attenuating chamber 636. The system 610 includes an elongate exhaust gas flow passageway 620 with an inlet end 622 and an opposite outlet end 624. The passageway 620 includes an upstream portion 626 disposed between its inlet end 622 and its outlet end 624, and a stub portion 628, which is axially aligned with the upstream portion 626. The stub portion 628 includes an inlet end 630 in gas flow communication with the upstream portion 626, and an opposite outlet portion 632. The downstream portion 634 of the passageway 620 is axially offset from the upstream portion 626 thereof, with the outlet end 624 of the passageway extending from the downstream portion 634 thereof.

The sound canceling chamber 636 has a single opening 638 in communication with the outlet end 632 of the stub 628 and upstream portion 626 of the passageway 620, with the chamber 636 and its opening 638 being in axial alignment with the stub 628 and upstream portion 626 of the passageway 620, as indicated by the axial centerline A. This allows the chamber 636 to receive incoming pressure pulses and reflect those pulses back up the upstream portion 626 of the passageway 620, generally as described for the embodiment 110 of FIG. 1 and other embodiments herein.

However, the sound attenuating or canceling chamber 636 has a different configuration than the corresponding chambers 136 through 536 of the embodiments of FIGS. 1 through 5. The chamber 636 includes opposite first and second branches, respectively 640 a and 640 b, extending generally laterally and orthogonally from the opening portion 638. This results in the chamber 636 having a generally “T” shaped configuration, with the base of the stem of the T comprising the opening end 638 of the chamber. The laterally offset branches 640 a, 640 b alter the pressure pulse reflective characteristics of the chamber 636, thereby altering the sound output of the system. It will be recognized that the branched chamber 636 may be incorporated with any of the other embodiments of the present invention, if so desired, or any of the chambers 136 through 536, or others described further below, may be incorporated with the gas flow system 610 of FIG. 6, if so desired.

FIG. 7 shows another relatively simple gas flow sound attenuation device 710 having a configuration much like that of the systems 110 of FIG. 1 and 610 of FIG. 6, but incorporating a differently configured branched sound attenuating chamber 736. The system 710 includes an elongate exhaust gas flow passageway 720 with an inlet end 722 and an opposite outlet end 724. The passageway 720 includes an upstream portion 726 disposed between its inlet end 722 and its outlet end 724, and a stub portion 728, which is axially aligned with the upstream portion 726. The stub portion 728 includes an inlet end 730 in gas flow communication with the upstream portion 726, and an opposite outlet portion 732. The downstream portion 734 of the passageway 720 is axially offset from the upstream portion 726 thereof, with the outlet end 724 of the passageway extending from the downstream portion 734 thereof.

The sound canceling chamber 736 has a single opening 738 in communication with the outlet end 732 of the stub 728 and upstream portion 726 of the passageway 720, with the chamber 736 and its opening 738 being in axial alignment with the stub 728 and upstream portion 726 of the passageway 720, as indicated by the axial centerline A. This allows the chamber 736 to receive incoming pressure pulses and reflect those pulses back up the upstream portion 726 of the passageway 720, generally as described for the embodiment 110 of FIG. 1 and other embodiments herein.

However, the sound attenuating or canceling chamber 736 has a different configuration than the corresponding chambers 136 through 636 of the embodiments of FIGS. 1 through 6. The chamber 736 includes opposite first and second branches, respectively 740 a and 740 b, extending generally parallel to one another from the opposite ends of an intermediate lateral chamber portion 742, which extends across the distal end of the opening neck portion 738. This results in the chamber 736 having a somewhat squared, generally “U” shaped configuration, with the base of the U comprising the laterally disposed portion 742 across the opening end 738 of the chamber.

It should also be noted that the opening end portion 738 of the sound canceling chamber 736 embodiment of FIG. 7 is of somewhat smaller diameter or cross sectional area than the remaining components 740 a, 740 b, and 742 of the chamber. The laterally offset branches 740 a, 740 b and smaller end portion 738 alter the pressure pulse reflective characteristics of the chamber 736, thereby altering the sound output of the system. It will be recognized that the branched chamber 736 may be incorporated with any of the other embodiments of the present invention, if so desired, or any of the chambers 136 through 636, or others described further below, may be incorporated with the gas flow system 710 of FIG. 7, if so desired.

FIG. 8 shows still another relatively simple gas flow sound attenuation device 810 having a configuration much like that of the systems 110 of FIG. 1, 610 of FIG. 6, and 710 of FIG. 7, but incorporating a differently configured branched sound attenuating chamber 836. The system 810 includes an elongate exhaust gas flow passageway 820 with an inlet end 822 and an opposite outlet end 824. The passageway 820 includes an upstream portion 826 disposed between its inlet end 822 and its outlet end 824, and a stub portion 828, which is axially aligned with the upstream portion 826. The stub portion 828 includes an inlet end 830 in gas flow communication with the upstream portion 826, and an opposite outlet portion 832. The downstream portion 834 of the passageway 820 is axially offset from the upstream portion 826 thereof, with the outlet end 824 of the passageway extending from the downstream portion 834 thereof.

The sound canceling chamber 836 has a single opening 838 in communication with the outlet end 832 of the stub 828 and upstream portion 826 of the passageway 820, with the chamber 836 and its opening 838 being in axial alignment with the stub 828 and upstream portion 826 of the passageway 820, as indicated by the axial centerline A. This allows the chamber 836 to receive incoming pressure pulses and reflect those pulses back up the upstream portion 826 of the passageway 820, generally as described for the embodiment 110 of FIG. 1 and other embodiments herein.

However, the sound attenuating or canceling chamber 836 has a different configuration than the corresponding chambers 136 through 736 of the embodiments of FIGS. 1 through 7. The chamber 836 includes opposite first and second branches, respectively 840 a and 840 b, extending generally parallel to one another from the opposite ends of an intermediate lateral chamber portion 842 which extends across the distal end of the opening neck portion 838. The intermediate crossmember portion 842 of the chamber 836 differs from the corresponding component 742 of the chamber 736 of FIG. 7, due to the swept or angled configuration of the crossmember 842 in FIG. 8. This results in the chamber 836 having a generally “Y” shaped configuration, with the stem of the Y comprising the opening end portion 838 of the chamber. The laterally offset branches 840 a, 840 b alter the pressure pulse reflective characteristics of the chamber 836, thereby altering the sound output of the system. It will be recognized that the branched chamber 836 may be incorporated with any of the other embodiments of the present invention, if so desired, or any of the chambers 136 through 736, or others described further below, may be incorporated with the gas flow system 810 of FIG. 8, if so desired.

It should be noted that the various sound canceling or attenuating chambers in the gas flow sound attenuation devices of the present invention need not have a uniform external shape. In some instances, a chamber having an irregular or non-uniform configuration, particularly such an internal configuration, may prove superior in canceling certain frequencies of sound. FIGS. 9 and 10 provide perspective views of two exemplary sound canceling chambers having polyhedral configurations.

The chamber 936 of FIG. 9 is defined by opposite, parallel and flat first and second panels 944 a and 944 b, with opposed, inwardly angled first and second lateral side wall panels 946 a and 946 b. (The panels are shown for only one side, with it being understood that the chamber 936 is laterally symmetrical.) The polyhedral chamber 936 includes a single opening 938 at one end thereof, with the opposite end being closed. The various panels 944 a through 946 b alter the pressure pulse reflective characteristics of the chamber 936, thereby altering the sound output of the system.

The chamber 1036 of FIG. 10 is defined by a series of flat panels 1044 a, 1044 b, 1044 c, 1044 d, etc., mating with one another along alternating convex and concave edges. Opposite, parallel and flat first and second lateral sidewall panels 1046 a and 1046 b form the sides of the chamber 1036. The polyhedral chamber 1036 includes a single opening 1038 at one end thereof, with the opposite side or end being closed. The various panels 1044 a through 1046 b alter the pressure pulse reflective characteristics of the chamber 1036, thereby altering the sound output of the system.

Any of the sound canceling chambers in the gas flow sound attenuation devices of the present invention may also be combined and/or enclosed within an external shell, if so desired, in order to provide a compact unit. This is particularly true of multiple chamber embodiments, such as that exemplified in FIG. 5.

FIG. 11 shows such a multiple chamber gas flow sound attenuation device 1110 enclosed within an external shell. The device 1110 comprises an inlet pipe or passage 1114, with a first gas flow passageway 1120 a branching therefrom. A second gas flow passage 1120 b branches from the first passageway, with a third passage 1120 c branching from the second passage, and a fourth passage 1120 d branching from the third passage. The final passage 1120 d includes a downstream portion 1134 branching therefrom, which terminates in an outlet passage end 1124. The inlet passage 1114 and the first through fourth passageways 1120 a through 1120 d each terminate in an axially aligned stub portion, respectively 1128 through 1128 d, with each stub having a sound attenuating chamber, respectively 1136 through 1136 d, axially aligned with and extending therefrom.

The entire above-described assembly is enclosed within an external shell 1148, with only the upstream or entry pipe 1114 and the opposite downstream passage or pipe 1134 and its outlet 1124 extending from the otherwise closed shell 1148. The various pipes and passages contained within the enclosure 1148 may include additional sound attenuation means if so desired, e.g., baffling, glass packing, etc., as desired. Alternatively, additional flow paths may be provided outwardly from the various passages within the device to allow gas to flow through the remainder of the shell volume, if so desired.

The various pipes and passageways of the gas flow sound attenuation devices may include additional sound attenuating means therein, as noted above. It is also possible to include internal baffling within any of the sound attenuating chambers of the gas flow sound attenuation devices. FIGS. 12 and 13 provide illustrations of exemplary internally baffled chambers.

The chamber 1236 of FIG. 12 includes a single upstream or entry pipe 1214, which extends into the otherwise closed chamber. However, the chamber includes a series of alternating baffles therein, respectively 1250 a through 1250 e. The various baffles may comprise flat, semicircular sheets, as shown, or other baffle configuration(s) as desired, in any practicable number and arrangement. The various baffles 1250 a through 1250 e alter the pressure pulse reflective characteristics of the chamber 1236, thereby altering the sound output of the system.

FIG. 13 shows yet another embodiment of a gas flow sound attenuation device of the present invention, comprising a chamber 1336 having opposed chevron baffles 1350 a and 1350 b therein. The first chevron baffle 1350 a includes a passage 1352 therethrough for the upstream or entry pipe 1314, which extends from the front of the canister. The opposite second chevron baffle 1350 b is devoid of any passages or perforations, to reflect pressure pulses back toward the opposite baffle 1350 a and entry pipe 1314. The chevron baffles 1350 a and 1350 b alter the pressure pulse reflective characteristics of the chamber 1336, thereby altering the sound output of the system.

The present inventors have performed a series of tests upon different vehicles, in order to quantify the reduction in sound level provided by the present gas flow sound attenuation device. Tables I-IV, provided below, clearly indicate the sound level reduction provided by the present invention.

TABLE I SOUND LEVEL (dB) 1999 CADILLAC SEVILLE STS 4.6 V-8 GAS FLOW SOUND ATTENUATION DEVICE, RPM RANGE BASE, dB dB  750 rpm (idle) 80 75 2500 rpm 91 85 3500 rpm 102 86 2500 rpm (hot system) 92 85  750 rpm (hot idle) 81 73 TEMPERATURE GAS FLOW SOUND ATTENUATION DEVICE RPM RANGE BASE TEMP ° F. ° F. 2500 rpm 370 93

TABLE II SOUND LEVEL (dB) 1999 FORD EXPLORER 4 × 4 4.0 V-6 GAS FLOW SOUND ATTENUATION DEVICE, RPM RANGE BASE, dB dB  750 rpm (idle) 74 65 2500 rpm 87 81 3500 rpm 88 79 2500 rpm (hot system) 89 82  750 rpm (hot idle) 74 65 TEMPERATURE GAS FLOW SOUND ATTENUATION DEVICE RPM RANGE BASE TEMP ° F. ° F. 2500 rpm 380 89

TABLE III SOUND LEVEL (dB) 2007 FORD TAURUS 3.0 V-6 GAS FLOW SOUND ATTENUATION DEVICE, RPM RANGE BASE, dB dB  750 rpm (idle) 74 71 2500 rpm 72 75 3500 rpm 86 77 2500 rpm (hot system) 73 76  750 rpm (hot idle) 70 72 TEMPERATURE GAS FLOW SOUND ATTENUATION DEVICE RPM RANGE BASE TEMP ° F. ° F. 2500 rpm 378 86

TABLE IV SOUND LEVEL (dB) 2001 SATURN SL1 1.9I I-4 GAS FLOW SOUND ATTENUATION DEVICE, RPM RANGE BASE, dB dB  750 rpm (idle) 76 74 2500 rpm 89 72 3500 rpm 82 77 2500 rpm (hot system) 88 73  750 rpm (hot idle) 77 72 TEMPERATURE GAS FLOW SOUND ATTENUATION DEVICE RPM RANGE BASE TEMP ° F. ° F. 2500 rpm 325 85

In the above tests, the gas flow sound attenuation device tested with the Cadillac Seville is similar in configuration to that shown in FIG. 4 of the drawings. The gas flow attenuation devices tested with the other vehicles are similar in configuration to that shown in FIG. 1 of the drawings. The engines of all vehicles were run until they reached normal operating temperatures for all tests. The first three sound level data points in each test were run in increasing RPM from idle to 3500, which resulted in the exhaust initially being at a relatively cooler temperature when starting from idle. The last two sound level data points, i.e., 2500 RPM and idle, were made after running the engine up to 3500 RPM. The “Base” referenced in the above Tables refers to the measured sound level of the stock exhaust system, before installing the gas flow sound attenuation device of the present invention. The final column in the sound Tables refers to the measured sound level of the exhaust system with the gas flow sound attenuation device installed for testing therein.

In the above Tables, the “Base” temperature refers to the temperature of the exhaust pipe temperature in the flow-through portion, upstream of the gas flow sound attenuation device. The final column in the temperature Tables refers to the temperature of the canister when installed for testing in the exhaust system. Ambient temperature during testing averaged about 78° F. The quality of the sound was affected positively by the gas flow sound attenuation devices, although this could not be quantified. Some vehicles produced a “burbling” sound, consistent with varying pressure pulsations, before the installation of the sound attenuation devices. The “burbling” sound was reduced dramatically or canceled completely by the installation of the gas flow sound attenuation devices during testing.

The gas flow sound attenuation device can be constructed of any material, or any combination of materials, suitable to its application.

In conclusion, the gas flow sound attenuation device, in its various embodiments, provides a means of canceling or greatly reducing the sound output of a volume of gas flowing through a pipe or duct without a corresponding increase in backpressure. While the gas flow sound attenuation device is particularly well suited for use in automotive and other internal combustion engine exhaust systems, it is also well suited for use in quieting heating, ventilating, and air conditioning systems where there are no combustion gases. It should be noted that other variations are possible, e.g., the addition of sound absorption material (glass fiber batts, etc.) in the canister or chamber. The device may also be modified by the installation of a diverter valve at the mouth or opening of the chamber to allow pressure pulses to enter the chamber or to close off the chamber to such pulses, thereby altering the sound output of the system accordingly. Electronic noise or sound canceling means may be installed in combination with the device, thereby resulting in even further gains in sound cancellation. Accordingly, the gas flow sound attenuation device will provide improved efficiencies in exhaust systems and corresponding increases in fuel efficiency when used in motor vehicle installations.

It is to be understood that the present invention is not limited to the embodiments described above, but encompasses any and all embodiments within the scope of the following claims. 

1. A gas flow sound attenuation device, comprising: at least one elongate gas flow passageway having: an inlet end; an outlet end opposite the inlet end; at least one upstream portion disposed between the inlet end and the outlet end; a stub portion axially aligned with the upstream portion, the stub portion having an inlet end communicating with the upstream portion and an outlet end opposite the inlet end; and at least one downstream portion axially offset from the upstream portion, the outlet end extending from the downstream portion; and a sound-canceling chamber having a single opening defined therein, the single opening connected to and communicating with the outlet end of the stub portion and in axial alignment therewith.
 2. The gas flow sound attenuation device according to claim 1, wherein said at least one elongate passageway comprises an exhaust gas flow passageway and said sound canceling chamber comprises an exhaust sound canceling chamber.
 3. The gas flow sound attenuation device according to claim 1, wherein said at least one elongate gas flow passageway comprises a plurality of elongate gas flow passageways and said sound canceling chamber comprises a plurality of chambers, each of the chambers being connected to a corresponding one of the gas flow passageways.
 4. The gas flow sound attenuation device according to claim 3, further including an external shell surrounding all of the gas flow passageways and sound canceling chambers, the shell having an inlet and an outlet communicating with the gas flow passageways.
 5. The gas flow sound attenuation device according to claim 1, wherein said sound canceling chamber has a plurality of branches.
 6. The gas flow sound attenuation device according to claim 1, wherein said sound canceling chamber has a cross-sectional area larger than the cross-sectional area of the single opening defined therein.
 7. The gas flow sound attenuation device according to claim 1, wherein said sound canceling chamber has a polyhedral external configuration.
 8. The gas flow sound attenuation device according to claim 1, wherein said sound canceling chamber has at least one internal baffle disposed therein.
 9. An internal combustion engine exhaust gas flow sound attenuation device, comprising: at least one elongate exhaust gas flow passageway having: an inlet end; an outlet end opposite the inlet end; at least one upstream portion disposed between the inlet end and the outlet end; a stub portion axially aligned with the upstream portion, the stub portion having an inlet end communicating with the upstream portion and an outlet end opposite the inlet end; and at least one downstream portion axially offset from the upstream portion, the outlet end extending from the downstream portion; and an exhaust sound-canceling chamber having a single opening defined therein, the single opening connected to and communicating with the outlet end of the stub portion and in axial alignment therewith.
 10. The internal combustion engine exhaust gas flow sound attenuation device according to claim 9, wherein said at least one elongate exhaust gas flow passageway comprises a plurality of elongate exhaust gas flow passageways and said exhaust sound canceling chamber comprises a plurality of chambers, each of the chambers being connected to a corresponding one of the exhaust gas flow passageways.
 11. The internal combustion engine exhaust gas flow sound attenuation device according to claim 10, further including an external shell surrounding all of the exhaust gas flow passageways and exhaust sound canceling chambers, the shell further having an inlet and an outlet each communicating with the exhaust gas flow passageways.
 12. The internal combustion engine exhaust gas flow sound attenuation device according to claim 9, wherein said exhaust sound canceling chamber has a plurality of branches.
 13. The internal combustion engine exhaust gas flow sound attenuation device according to claim 9, wherein said exhaust sound canceling chamber has a cross-sectional area larger than the cross-sectional area of the opening thereof.
 14. The internal combustion engine exhaust gas flow sound attenuation device according to claim 9, wherein said exhaust sound canceling chamber has a polyhedral external configuration.
 15. The internal combustion engine exhaust gas flow sound attenuation device according to claim 9, wherein said exhaust sound canceling chamber has at least one internal baffle disposed therein.
 16. An internal combustion engine exhaust gas flow sound attenuation device, comprising: a plurality of elongate gas flow passageways, each of the passageways having: an inlet end; an outlet end opposite the inlet end; at least one upstream portion disposed between the inlet end and the outlet end; a stub portion axially aligned with the upstream portion, the stub portion having an inlet end communicating with the upstream portion and an outlet end opposite the inlet end; at least one downstream portion axially offset from the upstream portion, the outlet end extending from the downstream portion; and an exhaust sound canceling chamber having a single opening therein, the single opening connected to and communicating with the outlet end of each stub portion and in axial alignment therewith; and an external shell surrounding all of the gas flow passageways and sound canceling chambers, the shell having an inlet and an outlet each communicating with the gas flow passageways.
 17. The internal combustion engine exhaust gas flow sound attenuation device according to claim 16, wherein at least one said exhaust sound canceling chamber has a plurality of branches.
 18. The internal combustion engine exhaust gas flow sound attenuation device according to claim 16, wherein at least one said exhaust sound canceling chamber has a cross-sectional area larger than the cross-sectional area of the opening thereof.
 19. The internal combustion engine exhaust gas flow sound attenuation device according to claim 16, wherein at least one said exhaust sound canceling chamber has a polyhedral external configuration.
 20. The internal combustion engine exhaust gas flow sound attenuation device according to claim 16, wherein at least one said exhaust sound canceling chamber has at least one internal baffle disposed therein. 